Version 3.0.1

Added

• PHP >=8.0 support in composer.json (fixes #13)
• GitHub Actions build status badge in README.md
• PHPStan in dev dependencies
• Additional build checks (PHPStan and PHP-CS)
• Automatic SVG badge generation for code coverage

Removed

• .travis.yml build support (switched to Github Actions)
• Build dependency on scrutinizer.org service